U.S. patent number 10,494,933 [Application Number 15/074,180] was granted by the patent office on 2019-12-03 for airfoil with multi-material reinforcement.
This patent grant is currently assigned to General Electric Company. The grantee listed for this patent is General Electric Company. Invention is credited to Gary Willard Bryant, Jr., Tod Winton Davis, Wei Wu.
United States Patent |
10,494,933 |
Bryant, Jr. , et
al. |
December 3, 2019 |
Airfoil with multi-material reinforcement
Abstract
An airfoil includes: an airfoil body having convex and concave
sides extending between a leading edge and a trailing edge, the
airfoil body including primary and secondary regions having
differing physical properties; and at least one metallic cladding
element attached to the airfoil body.
Inventors: |
Bryant, Jr.; Gary Willard
(Loveland, OH), Davis; Tod Winton (Liberty Township, OH),
Wu; Wei (Mason, OH) |
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Assignee: |
General Electric Company
(Schenectady, NY)
|
Family
ID: |
58277197 |
Appl.
No.: |
15/074,180 |
Filed: |
March 18, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170268349 A1 |
Sep 21, 2017 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D
5/147 (20130101); F01D 5/282 (20130101); F04D
29/324 (20130101); F05D 2220/36 (20130101); F05D
2240/304 (20130101); F05D 2240/303 (20130101); F05D
2240/307 (20130101); F05D 2300/603 (20130101) |
Current International
Class: |
F01D
5/28 (20060101); F01D 5/14 (20060101); F04D
29/32 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Extended European Search Report and Opinion issued in connection
with corresponding EP Application No. 17160480.4 dated Aug. 29,
2017. cited by applicant.
|
Primary Examiner: Shanske; Jason D
Assistant Examiner: Getachew; Julian B
Attorney, Agent or Firm: General Electric Davidson;
Kristi
Claims
What is claimed is:
1. An airfoil, comprising: an airfoil body having a root, a tip, a
convex side, and a concave side, the convex and concave sides
extending between a leading edge of the airfoil body and a trailing
edge of the airfoil body, the airfoil body comprising: a primary
region formed of a first composite material, the first composite
material encompassing an entire thickness of the airfoil body from
the convex side to the concave side; a secondary region comprising
an inner core and an outer skin of the airfoil body, the inner core
being formed of the first composite material and the outer skin
being formed of a second composite material having differing
material properties from the first composite material, the first
and second composite materials combining to encompass an entire
thickness of a portion of the airfoil body from the convex side to
the concave side; and a transition zone positioned between the
primary region and the secondary region, wherein a portion of the
outer skin extends into the transition zone such that in the
transition zone, a layer of the first composite material overlies
all of the second composite material extending into the transition
zone to create an interlocking joint; and at least one metallic
cladding element attached to the airfoil body.
2. The airfoil of claim 1 wherein each of the first and second
composite materials includes a matrix having reinforcing fibers
embedded therein.
3. The airfoil of claim 2 wherein at least one of the first and
second composite materials is a polymeric matrix composite having
carbon reinforcing fibers.
4. The airfoil of claim 3 wherein the second composite material is
a polymeric matrix composite having high-elongation reinforcing
fibers with an elongation greater than that of carbon fibers.
5. The airfoil of claim 4 wherein the high-elongation reinforcing
fibers comprise glass fibers.
6. The airfoil of claim 1 wherein the secondary region is disposed
adjacent to at least one free edge of the airfoil body.
7. The airfoil of claim 6 wherein the secondary region is disposed
adjacent to the leading edge or trailing edge of the airfoil body,
and covers one-third of a chord dimension of the airfoil.
8. The airfoil of claim 1 wherein the first composite material
comprises a polymeric matrix strengthened with carbon fibers and
the second composite material comprises a polymeric matrix
strengthened with glass fibers.
9. The airfoil of claim 8 wherein a portion of the secondary region
immediately adjacent to some or all of free edges of the airfoil
body comprises the second composite material formed of a polymeric
matrix with glass fibers through the entire thickness of the
airfoil body from the convex side to the concave side.
10. The airfoil of claim 1 wherein one of the at least one metallic
cladding elements is a leading edge guard attached to the leading
edge of the airfoil body, the leading edge guard comprising a nose
with spaced-apart first and second wings extending therefrom.
11. The airfoil of claim 1 wherein one of the at least one metallic
cladding elements is a tip cap attached to the tip of the airfoil
body, the tip cap comprising a pair of side walls extending along
the convex and concave sides of the airfoil body.
12. The airfoil of claim 11 wherein an exterior surface of the tip
cap acts as an aerodynamic extension of the airfoil body.
13. The airfoil of claim 11 wherein the tip cap is attached to the
airfoil body with an adhesive.
14. The airfoil of claim 11 wherein the tip cap includes a tip
portion and a trailing edge portion, the tip portion and trailing
edge portion collectively defining an L-shape.
15. The airfoil of claim 11 wherein the tip cap extends from the
tip of the airfoil body to a location one-half of a span of the
airfoil.
16. The airfoil of claim 14 wherein in the chordwise direction, the
trailing edge portion of the tip cap extends from the trailing edge
forward, covering one-third of a chord dimension of the airfoil
body.
17. An airfoil, comprising: an airfoil body having a root, a tip, a
convex side, and a concave side, the convex and concave sides
extending between a leading edge of the airfoil body and a trailing
edge of the airfoil body, the airfoil body comprising a primary
region, a transition zone, and a secondary region, the primary
region having differing material properties than the secondary
region; at least one metallic cladding element attached to the
airfoil body; wherein the primary region is formed of a first
composite material comprising a polymeric matrix strengthened with
carbon fibers, the first composite material encompassing an entire
thickness of the airfoil body from the convex side to the concave
side; wherein the secondary region is disposed adjacent to at least
one free edge of the airfoil body, the secondary region including
an inner core and an outer skin of the airfoil body, the inner core
being formed of the first composite material and the outer skin
being formed of a second composite material comprising a polymeric
matrix strengthened with glass fibers, the first and second
composite materials combining to encompass an entire thickness of a
portion of the airfoil body from the convex side to the concave
side; and wherein the transition zone is positioned between the
primary region and the secondary region, and wherein a portion of
the outer skin extends into the transition zone such that in the
transition zone, a layer of the first composite material overlies
all of the outer skin extending into the transition zone to create
an interlocking joint, the outer skin being reduced in thickness as
the outer skin extends from the secondary region into the
transition zone.
18. The airfoil of claim 17 wherein a portion of the secondary
region immediately adjacent to one or more of the free edges of the
airfoil body comprises the second composite material formed of a
polymeric matrix with glass fibers through the entire thickness of
the airfoil body from the convex side to the concave side.
19. The airfoil of claim 17 wherein one of the at least one
metallic cladding elements is a tip cap attached to the tip of the
airfoil body, the tip cap comprising a pair of side walls extending
along the convex and concave sides of the airfoil body.
20. The airfoil of claim 19 wherein the tip cap includes a tip
portion and a trailing edge portion, the tip portion and trailing
edge portion collectively defining an L-shape.
21. An airfoil, comprising: an airfoil body having convex and
concave sides extending between a leading edge of the airfoil body
and a trailing edge of the airfoil body, the airfoil body
comprising: a primary region formed of a first composite material
comprising a matrix having reinforcing fibers embedded therein, the
first composite material encompassing an entire thickness of the
airfoil body from the convex side to the concave side; a secondary
region comprising an inner core and an outer skin of the airfoil
body, the inner core being formed of the first composite material
and the outer skin being formed of a second composite material
having differing material properties from the first composite
material and comprising a matrix having reinforcing fibers embedded
therein, the first and second composite materials combining to
encompass an entire thickness of a portion of the airfoil body from
the convex side to the concave side; a transition zone positioned
between the primary region and the secondary region, wherein a
portion of the outer skin extends into the transition zone such
that in the transition zone, a layer of the first composite
material overlies all of the second composite material extending
into the transition zone to create an interlocking joint, the
second composite material being reduced in thickness in a staggered
configuration as the outer skin extends from the secondary region
into the transition zone; wherein the primary region has a first
elongation and the secondary region has a second elongation greater
than the first elongation; and a metallic cladding element attached
to the airfoil body, the metallic cladding element covering a
portion of the secondary region.
22. The airfoil of claim 21 wherein at least one of the first and
second composite materials is a polymeric matrix including carbon
reinforcing fibers.
23. The airfoil of claim 22 wherein the second composite material
is a polymeric matrix including high-elongation reinforcing fibers
having an elongation greater than that of carbon fibers.
24. The airfoil of claim 23 wherein the second composite material
is a polymeric matrix including glass reinforcing fibers.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to airfoils and in particular to
fan blades with multi-material reinforcement.
Fan blades and other structures used in turbine engine applications
are susceptible to foreign object impact damage, for example during
bird ingestion events ("bird strikes"). Blades made of composite
materials such as carbon fiber reinforced epoxy are attractive due
to their high overall specific strength, specific stiffness and
light weight. However, carbon composites are particularly prone to
brittle fracture and delamination during foreign object impacts due
to their low ductility. Blade leading edges, trailing edges, and
tips are particularly sensitive because of the generally lower
thickness in these areas and the well-known susceptibility of
laminated composites to free edge delamination.
For best aerodynamic performance, it is desirable to use fan blades
which are thin and have a long chord. One problem with such fan
blades is that higher strains are encountered in the event of a
bird strike as compared to thicker blades having a shorter
chord.
It is known to provide impact damage protection for composite fan
blades using metallic guards bonded thereto, also referred to as
metallic cladding. For example, fan blades are known as having a
composite body with metallic cladding extending over the leading
edge, the tip, and the trailing edge.
Metallic cladding is generally made of high-density alloys. One
problem with their use over extensive areas of an airfoil is that
their weight offsets the weight savings from the use of composite
material.
BRIEF SUMMARY OF THE INVENTION
At least one of the above-noted problems is addressed by an airfoil
made of composite material incorporating regions with material
having increased elongation properties, in combination with
metallic cladding.
According to one aspect of the technology described herein, an
airfoil includes: an airfoil body having convex and concave sides
extending between a leading edge and a trailing edge, the airfoil
body including primary and secondary regions having differing
physical properties; and at least one metallic cladding element
attached to the airfoil body.
According to another aspect of the technology described herein, an
airfoil includes: an airfoil body having a root and a tip, and
convex and concave sides extending between a leading edge and a
trailing edge, the airfoil body including primary and secondary
regions having differing material properties; and at least one
metallic cladding element attached to the airfoil body; wherein
within the primary region, the entire thickness of the airfoil body
includes a first composite material comprising a polymeric matrix
strengthened with carbon fibers; and wherein the secondary region
is disposed adjacent to at least one free edge of the airfoil body,
and within the secondary region, an inner core of the airfoil body
includes the first composite material, while an outer skin includes
a second composite material includes a polymeric matrix
strengthened with glass fibers.
According to another aspect of the technology described herein, an
airfoil includes: an airfoil body having convex and concave sides
extending between a leading edge and a trailing edge, the airfoil
body including primary and secondary regions, wherein each of the
primary and secondary regions includes a composite material
including a matrix having reinforcing fibers embedded therein, the
primary region having a first elongation, and the secondary region
having a second elongation greater than the first elongation; and a
first metallic cladding element attached to the body, the metallic
cladding element covering a portion of the secondary region.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be best understood by reference to the following
description taken in conjunction with the accompanying drawing
figures in which:
FIG. 1 is a side elevation view of an exemplary gas turbine engine
fan blade;
FIG. 2 is a cross-sectional view taken along lines 2-2 of FIG.
1;
FIG. 3 is a cross-sectional view taken along lines 3-3 of FIG. 1;
and
FIG. 4 is a cross-sectional view taken along lines 4-4 of FIG.
1.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings wherein identical reference numerals
denote the same elements throughout the various views, FIG. 1
depicts an exemplary fan blade 10 for a gas turbine engine. The fan
blade 10 includes an airfoil 12, shank 14, and dovetail 16. A
portion of the airfoil 12, along with the shank 14 and the dovetail
16, are part of a unitary airfoil body 17. The airfoil 12 extends
between a root 18 and a tip 20, and has a leading edge 22 and a
trailing edge 24. Opposed convex and concave sides 26 and 28,
respectively, extend between the leading edge 22 and the trailing
edge 24. The tip 20, the leading edge 22, and the trailing edge 24
can each be considered a "free edge" of the airfoil body 17. The
fan blade 10 is merely an example; the principles of the present
invention are applicable to other kinds of structures requiring
impact protection.
The airfoil body 17 is made from a composite material, defined
herein as a material including two or more distinct materials
combined into one structure, for example a matrix having
reinforcing fibers embedded therein. One example of a composite
system suitable for use in aerospace applications includes an epoxy
matrix with carbon fiber reinforcement.
More specifically, the airfoil body 17 incorporates two or more
regions wherein each region comprises a unique composite system. A
primary region 30 is made from a first composite system having a
first set of physical properties that includes a first stiffness
and a first elongation. "Elongation" as used herein refers to the
increase in gage length of a material specimen before tensile
failure. This increase may be expressed as a percentage of the
original gage length. This usage is consistent with the commonly
accepted definition of the term. In the illustrated example the
primary region 30 comprises an epoxy matrix with carbon reinforcing
fibers. In general the primary region 30 extends throughout the
majority of the airfoil body 17.
The airfoil body 17 may incorporate one or more secondary regions.
The secondary regions, designated 32 collectively, are made from a
second composite system having a second set of physical properties
that includes a second stiffness and a second elongation. More
specifically, the second stiffness is less than the first
stiffness, and the second elongation is greater than the first
elongation. Stated another way, each secondary region 32 is less
stiff (and may be weaker in terms of yield stress and/or ultimate
tensile stress) than the primary region 30, but allows more
deflection or strain to failure. In the illustrated example, some
or all of each secondary region 32 comprise an epoxy matrix with
reinforcing fibers having greater elongation than carbon fibers,
referred to generally herein as "high-elongation" fibers. One
non-limiting example of a high-elongation fiber is glass fiber. For
example, glass fibers commercially available as "E-glass" or
"S-glass" may be used for this purpose. In general each secondary
region 32 extends over a relatively small portion of the airfoil
body 17, preferably a portion that is subject to high strains
during an impact.
In the illustrated example, three different potential secondary
regions 32A, 32B, and 32C are shown. The boundaries of these
potential secondary regions 32A, 32B, and 32C are delineated by
dashed lines. Each secondary region 32A, 32B, and 32C is disposed
adjacent to one or more of the free edges of the airfoil body 17,
including the tip 20, the leading edge 22, and the trailing edge
24. A first example secondary region is labeled 32A. In the radial
direction, the secondary region 32A begins at a location
approximately 1/4 of the span "S" of the fan blade 10 away from the
root 18, and extends to the tip 20 of the fan blade 10. In the
chordwise direction, the secondary region 32A extends from the
trailing edge 24 forward, from the leading edge 22 aftward,
covering approximately 1/3 of the chord dimension "C" of the fan
blade 10. These dimensions can be varied to suit a particular
application.
A second example secondary region is labeled 32B and is positioned
adjacent to the tip 20. From the tip 20, the second secondary
region 32B extends radially to cover 1/4 of the span S and covers
the entire chord dimension C.
A third example secondary region is labeled 32C and is positioned
adjacent to the leading edge 22. In the radial direction, the
secondary region 32C begins at a location approximately 1/4 of the
span S away from the root 18, and extends to the tip 20. In the
chordwise direction, the secondary region 32C extends from the
leading edge 24 aftward, covering approximately 1/3 of the chord
dimension C.
Any or all of the example secondary regions 32A, 32B, and 32C
described above may be implemented individually or in combination.
For example, a single, large secondary region designated 32 having
an inverted "U" shape may be provided, representing the union of
all three secondary regions 32A, 32B, and 32C.
As a general principle, it is desirable to limit the size of the
secondary regions 32 because of their lower strength. Furthermore,
as a general principle, it is desirable to locate the intersection
of the primary region 30 and the secondary regions 32 in an area
that is not subject to high stresses. Accordingly, the exact size
and shape of the secondary regions 32 may be determined on a
case-by-case basis.
FIG. 2 illustrates the construction of the primary and secondary
regions 30, 32 in more detail. This view is representative of the
construction of a single collective U-shaped secondary region 32,
as well as any of the individual secondary regions 32A, 32B, or 32C
described above. In the primary region 30, the entire thickness of
the airfoil body 17 comprises a first composite material 34 such as
an epoxy matrix strengthened with carbon fibers. In the secondary
region 32, the inner core of the airfoil body 17 comprises the
first composite material 34, while an outer skin comprises a second
composite material 36 such as an epoxy matrix strengthened with
high-elongation fibers, for example E-glass or S-glass fibers. The
relative thickness of the different reinforcing fibers may be
varied to suit a particular application. In the illustrated
example, a small portion of the airfoil body 17 immediately
adjacent to the free edge (trailing edge 24 shown) comprises an
epoxy matrix with high-elongation fibers through its entire
thickness.
A transition zone 38 may be provided between the first and
secondary regions 30, 32 in order to avoid stress concentrations at
the junctures between dissimilar materials. In the illustrated
example, the thickness of the second composite material 36 is
reduced in a staggered, "stair-stepped" configuration within the
transition zone 38. Additionally, a layer of the first composite
material 34 overlies the second composite material 36 within the
transition zone 38 in order to create an interlocking joint. The
exact transition of the staggered, "stair-stepped" pattern is
determined on a case-by-case basis, given different coverage areas
of first and second composite material.
The primary and secondary regions 30, 32 may be manufactured
concurrently, for example by providing a layup of the desired
configuration of reinforcing fibers, infiltrating the fiber layup
with uncured resin, and then curing the resin.
In addition to the high-elongation fibers, the fan blade 10 also
incorporates at least one metallic cladding element. In the
specific example shown in FIG. 1, the cladding elements comprise a
leading edge guard 40 and a tip cap 42.
The leading edge guard 40 is attached to the leading edge 22. The
leading edge guard 40 provides the fan blade 10 with additional
impact resistance, erosion resistance and improved resistance of
the composite structure to delamination.
As best seen in FIG. 3, the leading edge guard 40 comprises a nose
44 with a pair of wings 46 and 48 extending aft therefrom. The
wings 46 and 48 taper in thickness as they extend away from the
nose 44. Exterior surfaces of the nose 44 and wings 46 and 48
collectively define an exterior surface 50 of the leading edge
guard 40. The shape and dimensions of the exterior surface 50 are
selected to act as an aerodynamic extension of the airfoil body 17.
Stated another way, the exterior shape of the airfoil 12 is defined
in part by the airfoil body 17 and in part by the leading edge
guard 40. The leading edge guard 40 may be attached to the airfoil
body 17 with a known type of adhesive.
Interior surfaces of the nose 44 and wings 46 and 48 collectively
define an interior surface 52 of the leading edge guard 40. The
shape and dimensions of the interior surface 52 are selected to
closely fit the exterior of the airfoil body 17.
The leading edge guard 40 may be made from a metal alloy of a
composition providing desired strength and weight characteristics.
Non-limiting examples of suitable alloys for construction of the
leading edge guard 40 include titanium alloys and nickel
alloys.
The tip cap 42 overlies portions of the convex and concave sides
26, 28 adjacent to the tip 20. The tip cap 42 provides additional
impact protection, as well as stiffens the airfoil body 17 in the
free edge regions of the tip and trailing edge 24. As best seen in
FIG. 4, the tip cap 42 includes a pair of side walls 56 and 58. The
exterior surfaces of the side walls 56 and 58 collectively define
an exterior surface 60 of the tip cap 42. The shape and dimensions
of the exterior surface 60 are selected to act as an aerodynamic
extension of the airfoil body 17. Stated another way, the exterior
shape of the airfoil 12 is defined in part by the airfoil body 17
and in part by the tip cap 42. The tip cap 42 may be attached to
the airfoil body 17 with a known type of adhesive.
As viewed in side elevation (FIG. 1), the tip cap 42 includes a tip
portion 62 and a trailing edge portion 64. The two portions 62 and
64 roughly define an L-shape. An upper forward edge 66 of the tip
cap 42 abuts the leading edge guard 40. An upper aft edge 68 of the
tip cap 42 follows the trailing edge 24 of the airfoil body 17. A
lower aft edge 70 of the tip 20 extends from the upper aft edge 68
axially forward and radially inward. A lower forward edge 72 of the
tip cap 42 interconnects the lower aft edge 68 and the upper
forward edge 66.
Interior surfaces of the side walls 56 and 58 collectively define
an interior surface 74 of the tip cap 42 (see FIG. 4). The shape
and dimensions of the interior surface 74 are selected to closely
fit the exterior of the airfoil body 17.
In the radial direction, the trailing edge portion 64 begins at the
tip 20 of the fan blade 10, and extends to a location approximately
1/2 of the span S of the fan blade 10 in the chordwise direction,
the trailing edge portion 64 extends from the trailing edge 24
forward, covering approximately 1/3 of the chord C of the fan blade
10. The tip cap 42 may or may not overly a portion of the secondary
region 32 as these dimensions can be varied to suit a particular
application. As a general principle, it is desirable to limit the
size of the tip cap 42 in order to minimize its weight.
The tip cap 42 may be made from a metal alloy of a composition
providing desired strength and weight characteristics. Non-limiting
examples of suitable alloys for construction of the tip cap 42
include titanium alloys and nickel alloys.
The fan blade 10 described above incorporates the beneficial
properties of composite and metallic materials to maximize the
impact capability and aerodynamic performance, while minimizing the
overall weight of the blade.
The incorporation of high-elongation fibers in the composite body
provides a higher strain to failure capability compared to the use
of carbon fibers only. The use of the metallic tip cap reduces any
additional deflection of the blade that may be caused by the
relatively less stiff composite material. The incorporation of the
high-elongation fibers permits the tip cap to be significantly
smaller than would otherwise be required in a conventional
composite airfoil using only carbon fiber. This will provide a
weight savings with accompanying improvement in engine
efficiency.
The foregoing has described an airfoil with multi-material
reinforcement. All of the features disclosed in this specification
(including any accompanying claims, abstract and drawings), and/or
all of the steps of any method or process so disclosed, may be
combined in any combination, except combinations where at least
some of such features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including any
accompanying claims, abstract and drawings) may be replaced by
alternative features serving the same, equivalent or similar
purpose, unless expressly stated otherwise. Thus, unless expressly
stated otherwise, each feature disclosed is one example only of a
generic series of equivalent or similar features.
The invention is not restricted to the details of the foregoing
embodiment(s). The invention extends to any novel one, or any novel
combination, of the features disclosed in this specification
(including any accompanying potential points of novelty, abstract
and drawings), or to any novel one, or any novel combination, of
the steps of any method or process so disclosed.
* * * * *